1. Field of the Invention
The present invention relates to fluidic dispensing devices, and, more particularly, to a fluidic dispensing device, such as a microfluidic dispensing device, having a diaphragm to control backpressure.
2. Description of the Related Art
One type of microfluidic dispensing device, such as an ink jet printhead, is designed to include a capillary member, such as foam or felt, to control backpressure. In this type of printhead, the only free fluid is present between a filter and the ejection device. If settling or separation of the fluid occurs, it is almost impossible to re-mix the fluid contained in the capillary member.
Another type of printhead is referred to in the art as a free fluid style printhead, which has a movable wall that is spring loaded to maintain backpressure at the nozzles of the printhead. One type of spring loaded movable wall uses a deformable deflection bladder to create the spring and wall in a single piece. An early printhead design by Hewlett-Packard Company used a circular/cylindrical deformable rubber part in the form of a thimble shaped bladder positioned between a container lid and a body. The thimble shaped bladder maintained backpressure in the ink enclosure defined by the thimble shaped bladder by deforming the bladder material as ink was delivered to the printhead chip. More particularly, in this design, the body is relatively planar, and a printhead chip is attached to an exterior of the relatively planar body on an opposite side of the body from the thimble shaped bladder. The thimble shaped bladder is an elongate cylindrical-like structure having a distal sealing rim that engages the planar body to form the ink enclosure. Thus, in this design, the sealing rim of the thimble shaped bladder is parallel to the printhead chip. A central longitudinal axis of the container lid and thimble shaped bladder extends though the location of the printhead chip and the corresponding chip pocket of the body. The deflection of the thimble shaped bladder collapses on itself, i.e., around and inwardly toward the central longitudinal axis.
What is needed in the art is a fluidic dispensing device having a diaphragm configured to control backpressure in a fluid reservoir of the fluidic dispensing device.